It is well known in the food industry that the addition of flavouring ingredients contribute to a major extent to the palatability of consumable edible materials; consequently, it is paramount to ensure the production of food products which are of consistent flavour quality and are thus attractive to consumers. This can be achieved by ensuring proper flavour release. In effect, taste and aroma are greatly influenced by volatile components present in such products. However, because of the volatility of these compounds, it is not easy to ensure that the predetermined critical amounts of each flavour components be present in the food and products as they reach the consumer. Losses of volatile components might occur during storage prior to incorporation into the food product, during mixing of the flavour component with the other food ingredients, during food processing, cooking, baking, during transportation and storage and finally during the preparation of the food product by the consumer himself.
These losses of volatile components from the food products may produce undesirable variations in the taste and aroma of the products as perceived by the consumer. On the other hand, losses of volatile components might occur through the conversion of certain flavour materials into unwanted less desirable or tasteless chemicals by their interaction with reagents present in the environment. Oxygen is an example of this type of reagent as it promotes the conversion of several labile flavour materials of current and critical utilization in the industry.
It is not surprising therefore to observe that, in order to reduce or eliminate the aforementioned problems associated with volatile and labile flavour components, various attempts have been made to encapsulate such components in certain carbohydrate matrices so as to reduce the volatility or lability of the components. This results in the preparation of stable free flowing powders containing the flavour compositions for later flavour release when incorporated into the food products or when the food product is eventually consumed.
Typical examples of flavour fixation on carbohydrate matrices are provided in U.S. Pat. Nos. 3,314,803; 3,554,768 and 3,736,149. These patents are mainly concerned with the problem associated with the stability of acetaldehyde in different flavour systems. For instance, U.S. Pat. No. 3,554,768 suggests the use of lactose, lactose-maltose, larch-gum, tapioca dextrin and gum Arabic as matrices for encapsulation of acetaldehyde by the method of spray-drying.
U.S. Pat. No. 3,736,149 discloses flavouring compositions which comprise a flavouring agent including acetaldehyde fixed in a matrix material containing lactose, a hydrocolloid gum and a starch hydrolysate.
U.S. Pat. No. 2,809,895 describes a process for encapsulation of an essential oil, such as lemon, lime or grapefruit oils, in a matrix comprising corn syrup, antioxidant and dispersing agent. The essential oil, antioxidant and dispersing agent are added to the corn syrup, and resultant mixture is heated to 85xc2x0-125xc2x0 C. and agitated or extruded to form an emulsion in pellet form, and the resulting particles are washed with a solvent and finally dried.
U.S. Pat. No. 3,703,137 described an essential oil composition formed by mixing oil with an antioxidant, separately mixing water, sucrose and hydrolyzed cereal solids with DE below 20, emulsifying the two mixtures together, extruding the resulting mixture in the form of rods into a solvent, removing the excess solvent and finally, adding an anti-caking agent.
U.S. Pat. Nos. 4,610,890 and 4,707,367 describe a process for preparing a solid essential oil composition having a high content of the essential oil, which composition is prepared by forming an aqueous solution containing a sugar, a starch hydrolysate and an emulsifier. The essential oil is blended with the aqueous solution in a closed vessel under controlled pressure to form an homogeneous melt, which is then extruded into a relatively cold solvent, dried and combined with an anti-caking agent.
The above-mentioned patents are merely illustrative of the considerable volume of patent literature related to the fixation of flavour ingredients in various matrices.
In essence, all of the above patents disclose the encapsulation of flavour materials in glass like polymeric materials. The understanding of the glassy state and its importance in food products has been considerably extended in recent years. Several methods of creating glass like states have been reported including the shock cooling of a polymeric melt to create a vitreous solidified matrix and more recently the use of extrusion cooking as a means of melting and intermixing a polymeric base material with the flavourant or other material to be encapsulated and then extrusion of this viscous material into a cooling system thus entrapping the flavourant within the matrix.
U.S. Pat. No. 5,009,900 describes such a process, a key embodiment of which is the requirement that the resulting encapsulated flavour has a glass transition temperature (Tg) significantly above the temperature at which it is stored and used. The critical temperature was recognized as being of at least 40xc2x0 C.
The concept of glass transition temperature is well described in the literature.
It represents the transition temperature from a rubbery phase to a glass; such a transition is characterised by a rapid increase in viscosity over several orders magnitude, over a rather small temperature range. It is recognized by many experts in the field that in the glassy state, i.e. at temperatures below Tg, all molecular translation is halted and it is this process which provides such effective entrapping of the flavour volatiles and prevention of other chemical events such as oxidation.
Implicit in much of the literature is the converse, namely that at temperatures above Tg, the encapsulation of flavour molecules will be ineffective and hence the importance of creating polymeric encapsulating materials with Tg values above ambient temperature.
We have discovered that, contrary to this prior assumption, it is possible to create materials which have glass transition temperatures below ambient temperature and which nevertheless are preferably effective at entrapping and stabilising flavouring systems over long periods of time.
Furthermore, the resulting particulate flavour compositions are less hygroscopic than the materials currently available.
The present invention provides a process for the preparation of particulate flavour compositions comprising a flavour oil fixed in a particulate polyol material, which process comprises:
a. mixing a mono- or disaccharide, a polysaccharide and water with a minor but flavour effective amount of a flavour oil to form a homogeneous substrate such that the resulting particulate flavour compositions possess a Tg below room temperature; and
b. extruding said homogeneous substrate at a temperature sufficient to form a melt which on cooling solidifies as a hard rubbery and amorphous material having said flavour oil entrapped therein.